Imaging apparatus, such as laser printers, typically comprise complex electrophotographic apparatus which are utilized to form an initial electrostatic latent image of the image which is to be printed. The electrostatic latent image is then developed by means of a liquid or powder toner, and the developed image is transferred either directly or indirectly to a final substrate.
U.S. Pat. No. 4,014,693 to Clark describes a method for forming a colored liquid deposit in image configuration on a surface without forming an initial electrostatic latent image. The method utilizes liquids which are electroviscous, i.e. whose viscosity changes as a function of the application of an electric field across them. In the Clark patent, images are deposited on a substrate by selectively applying specific voltages across such electroviscous liquids, such that at one voltage the liquid jells while at another voltage the liquid flows.
U.S. Pat. No. 4,504,138 describes a method of developing a latent imaging which includes applying a thin viscous layer of toner particles onto the circumferential surface of a rotating roller and bringing the layer so formed to a rotating photoconductive drum having a latent electrostatic image formed thereon. Transfer of portions of the toner layer then occurs as a function of the various voltages on the image and background portions of the latent image.
U.S. Pat. No. 3,623,122 describes a system in which a moving probe or a series of stationary probes are arranged to form a liquid toner image on a substrate. The liquid developer used in the apparatus has a solids concentration of 0.5% and apparently prints using electrophoretic deposition of toner particles on the substrate.